HSQ: Approxomately 10.7 "Holy FUCK"s per chapter, at a very conservative readthrough.
Hype Backlash: Inevitable for a story so well-regarded in the fandom.
Moral Event Horizon: Just in case you had any thoughts that maybe Zirah was like our old Lovable Rogue friend Crowley from the original... The spare baby doesn't get to live this time.
Nightmare Fuel: Getting there by the first chapter after the prologue. "Zirah would kill a baby just to stop him crying"... made even worse because he still suffers from Cuteness Proximity. It's just creepy.
"Creepy" sells Zirah a million miles short of the pants-wetting, throat-constricting, limb-trembling horror that he is capable of.
Tear Jerker: Seriously, this story WILL reduce you to a sobbing wreck.
Tough Act to Follow: The OTHER reason "what if Aziraphale fell instead of Crowley" fics aren't too common in the fandom — not only does this fic Deconstruct the concept so epically, it's so good that not many people want to risk trying their hand at the same concept and getting negatively compared to this story.
The Woobie: Caphriel. Okay, he's generally pretty stoic about it, but read that last chapter and tell me you don't want to give him a hug, thank him for everything he's done, and let Canon!Aziraphale fuss over him for a while.